Hormones produced by the hypothalamic-pituitary axis (HP) are released by neurones which are modulated by monoaminergic neurotransmitters; moreover, these hormones can directly affect central biogenic amine function, producing distinct behavioral effects. This crucial interface between central nervous system function and neuroendocrine secretory systems is providing a basis for new methods in the study of psychiatric illness. Current studies concentrate on dynamic tests of HP function, measurement and administration of behaviorally active peptides, elucidation of the temporal organization of neuroendocrine function, and the relationship of neuroendocrine function to sleep and its disorders. Major findings this year are as follows: dopamine infusion significantly elevates plasma and platelet MAO; lithium blunts prolactin rebound following dopamine infusion suggesting a modulating effect on dopaminergic function in man; prolactin and gonadotropin response to dopamine in patients on neuroleptics resembles responses seen in depression; growth hormone administration diminishes stage IV sleep; amenorrheic depressed women show neuroendocrine responses compatible with increased functional serotonergic activity.